Effects of aluminum exposure on the adherence, chemotaxis, and phagocytosis capacity of peritoneal macrophages in rats

Aluminum promotes B1 cells to produce IL-10 and impairs adaptive immune system

Aluminum (Al) is a metal existing in the human body, yet the immunotoxicity of Al remains elusive. To investigate the immunotoxicity of Al, C57BL/6 mice were treated with 200 or 800 ppm Al via drinking water for 3 months, and thereafter the adaptive immune system was evaluated. In addition, mouse splenocytes and human peripheral blood mononuclear cells (PBMC) were treated with Al in vitro to assess the impact of Al in vitro. Treatment with Al reduced the production of IgM and IgG in the serum, and the activation of B cells, CD4 T cells and CD8 T cells in the spleen of mice; treatment with Al in vitro suppressed the production of IgM and IgG, and the activation of B cells, CD4 T cells and CD8 T cells in mouse splenocytes and human PBMC. In vitro co-culture assays suggested that the suppressed adaptive immunity was due to B cells modified by Al. In terms of mechanism, a direct action of Al on B1 cells induced the B1 cells to be IL-10-producing cells and thereby suppressed the adaptive immune system, which was critically dependent on the Jak1/3-STAT signaling. This study reveals that Al suppresses the adaptive immunity via induction of IL-10-producing B1 cells.

Obesity and metabolic syndrome related macrophage promotes PD-L1 expression in TNBC through IL6/JAK/STAT pathway and can be reversed by telmisartan

Breast cancer is the most common malignant tumor in women. Its incidence is associated with obesity and metabolic syndrome (MetS), which are highly prevalent world widely and have been identified as poorer prognosis factors in breast cancer including triple-negative breast cancer (TNBC), which has poorer response to chemotherapy, radiotherapy, and endocrine therapy. Programmed death ligand 1 (PD-L1) is one of the immune checkpoints ligands that facilitates tumor escape and progress. Obesity/MetS could cause systemic inflammation and immune disorders, however, whether and how obesity/MetS affect PD-L1 expression in breast cancer had not been clarified. In the present study, we examined the PD-L1 expression profile in breast cancer either in online database or cell lines. We found higher PD-L1 mRNA level but not DNA copy number in breast cancer than normal breast tissue, and higher PD-L1 expression in TNBC than other subtypes. Moreover, we found a positive relationship between PD-L1 expression in TNBC and metabolic complications in patients. Next, obesity/MetS related M1 macrophage was found to promote the expression of PD-L1 in breast cancer cells cocultured with polarized macrophages derived from either monocyte-like cell line THP-1 or Wistar rat models. IL6/JAK/STAT pathway was further identified to be involved in the process. In addition, we discovered that the PD-L1 expression promoted by obesity/MetS could be restored by telmisartan, one of the angiotensin II receptor blockers (ARBs) and could affect macrophage polarization, through its selective peroxisome proliferator-activated receptor-gamma (PPARG) activation and NFKB p65 inhibition and therefore downregulates IL6 secretion from M1 macrophage.

Environmentally relevant doses of tetrabromobisphenol A (TBBPA) cause immunotoxicity in murine macrophages

TBBPA is one of the main brominated flame retardants and is ubiquitous in the environment. TBBPA can directly encounter immune cells via the bloodstream, posing potential immunotoxicity. To understand the immunomodulating effect of TBBPA on macrophages, the murine macrophages, RAW 264.7, were exposed to TBBPA at environmentally relevant concentrations (1-100 nM). The results showed that TBBPA at the selected concentrations did not alter cell viability of RAW 264.7 cells with or without LPS stimulation. TBBPA upregulated the expression of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α, whereas it attenuated the LPS-stimulated expression of these pro-inflammatory cytokines, and the expression of anti-inflammatory cytokines, including IL-4, IL-10, and IL-13. In addition, TBBPA reduced the mRNA levels of antigen-presenting-related genes, including H2-K2, H2-Aa, Cd80, and Cd86. Moreover, TBBPA impaired the phagocytic activity of macrophages. Furthermore, exposure to TBBPA significantly elevated the protein levels of phosphorylated NF-κB p65 (p-p65), while it reduced LPS-stimulated p-p65 protein levels. DCFH-DA staining assays showed that TBBPA caused a slight but significant elevation in reactive oxygen species levels. The data obtained in the present study demonstrated that exposure to environmentally relevant concentrations of TBBPA posed immunotoxicity in macrophages and unveiled a potential health risk of TBBPA.

β2 Adrenergic Regulation of the Phagocytic and Microbicide Capacity of Macrophages from Obese and Lean Mice: Effects of Exercise

Macrophages are crucial in the inflammation associated with obesity. Exercise is the main non-pharmacological strategy against obesity, not only for improving metabolic impairment, but also because of its anti-inflammatory effects, particularly those mediated by β2 adrenergic receptors (β2-AR). Nevertheless, these anti-inflammatory effects could immunocompromise the innate response against pathogen challenge. Thus, the objective of this work was to evaluate the effect of obesity, and of exercise in this condition, on the β2 adrenergic regulation of the innate function of macrophages. High fat diet-induced obese C57BL/6J mice were used to evaluate the effects of acute and regular exercise on the phagocytic and microbicide capacities of peritoneal macrophages. Selective β2-AR agonist terbutaline (1 µM) decreased the phagocytic and microbicide activities of macrophages from control lean and obese sedentary animals. While acute exercise did not modify the inhibitory capacity of terbutaline, regular exercise abolished this inhibitory effect. These effects cannot be explained only by changes in the surface expression of β2-AR. In conclusion, (1) obesity does not alter the β2-AR-mediated decrease of the innate response of macrophages and (2) regular exercise can revert the inhibitory effect of terbutaline on the phagocytic activity of macrophages, although obesity seems to hinder this immunophysiological adaptation.

Chlorogenic acid protects against aluminum toxicity via MAPK/Akt signaling pathway in murine RAW264.7 macrophages

Aluminum (Al), which may bring about damage to the macrophages, has been implicated in the development of immunological diseases. It has been reported that chlorogenic acid (CGA, 5‑caffeoylquinic acid, chemical formula: C₁₆H₁₈O₉) is a natural antioxidant and chelating agent with the capacity against Al (III)-induced biotoxicity. The present study was carried out to investigate whether CGA could reduce AlCl₃-induced cellular damage in RAW264.7 cells. After treatment with AlCl₃, the inhibition rate of viability and phagocytic activity of RAW264.7 cells was 54.5% and 27.6%, respectively. Administration of CGA significantly improved the integrity and phagocytic activity, and attenuated the accumulation of intracellular Al(III) level and oxidative stress in Al(III)-treated cells. Furthermore, CGA significantly inhibited Al(III)-induced increase of phospho-Jun N-terminal kinase (p-JNK), a pro-apoptotic Bcl-2 family protein (Bad), cytochrome c and decrease of extracellular regulated protein kinases (ERK1/2), protein kinase B (Akt) protein expressions. These results showed that CGA has a protective effect against Al(III)-induced cytotoxicity through mitogen-activated protein kinase (MAPK)/Akt-mediated caspase pathways in RAW264.7 cells.

AlCl3 inhibits LPS-induced NLRP3 inflammasome activation and IL-1β production through suppressing NF-κB signaling pathway in murine peritoneal macrophages

Aluminum (Al), a common environmental pollutant, has been reported to inhibit the immune functions of macrophage. However, the mechanisms involved remain unclear. In this study, murine peritoneal macrophages were exposed to 0, 0.27, 0.54, and 1.08 mg/mL of aluminium chloride (AlCl₃) for 24 h, and then treated with 1 μg/mL lipopolysaccharide (LPS) for another 6 h. No addition of both AlCl₃ and LPS serviced as control group. We observed that AlCl₃ has cytotoxicity in murine peritoneal macrophages, showing a decrease in cell viability and an increase in lactate dehydrogenase release. Besides, AlCl₃ exposure restrained the LPS-induced NLR pyrin domain containing 3 (NLRP3) inflammasome activation presented as NLRP3 expressions reduction, caspase-1 cleavage inhibition and interleukin 1 beta (IL-1β) maturation lessened. Meanwhile, AlCl₃ exposure decreased LPS-induced IKKβ activity, IκBα phosphorylation, the phosphorylation and mRNA expression of NF-κB p65, as well the genes expression and concentration in medium supernatant of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). The results suggested that AlCl₃ inhibited the activation of NF-κB signaling pathway induced by LPS, which maybe one of the upstream signals involved in the inhibition of NLRP3 inflammasome activation by AlCl₃. This research can provide theoretical basis for understanding the immune toxicity of Al, and deepening the cognition of Al exposure hazards to immune response.

Effect of silicon-rich water intake on the systemic and peritoneal inflammation of rats with chronic low levels of aluminum ingestion

BACKGROUND AND OBJECTIVES

Study evaluated effect of silicon-rich water intake on systemic inflammation and functional characteristics of peritoneal macrophages (PMs) of rats that were chronically exposed to dietary aluminum.

METHODS

One month-old female Wistar Albino rats were administered aluminum chloride dissolved in distilled water (1.6mg/kg body weight in 0.5mL) by gavage for 90days. The rats were then given standard (6mg/L) or silicon-rich water (19mg/L silicon) (n=7/group). Control rats underwent sham gavage and received standard or silicon-rich water (n=7/group). Blood was assessed for cytokine levels. Unstimulated and lipopolysaccharide (LPS)-stimulated PMs were assessed in terms of phagocytic activity and cytokine secretion in vitro.

RESULTS

Chronic exposition to dietary aluminum and silicon-rich drinking water did not change serum TNF-α levels. Aluminum increased serum IL-2 and this was reversed by silicon-rich water. The aluminum-exposed rats had higher serum sICAM-1 than sham-gavaged, unrelated to type of water. LPS-stimulated PMs from aluminum-intoxicated animals exhibited low phagocytic activity and release of TNF-α, this was significantly improved by silicon-rich water intake. In the presence of silicon-rich water, LPS-stimulated and unstimulated PMs from aluminum-exposed rats produced significantly more IL-10.

CONCLUSIONS

Chronic ingestion of aluminum, increases systemic and peritoneal inflammation and PM dysfunction. The presence of high levels of the natural aluminum antagonist silicon in the drinking water restored IL-10 and TNF-α PM secretion, preventing prolonged inflammation. Thus, silicon intake can decrease the immunotoxicity of aluminum.

The immunotoxicity of aluminum trichloride on rat peritoneal macrophages via β2-adrenoceptors/cAMP pathway acted by norepinephrine

The previous research found that norepinephrine (NE) enhanced the immunotoxicity of aluminum trichloride (AlCl3) on rat peritoneal macrophages in vitro through activating the β2-adrenoceptors (β2-AR)/cAMP pathway. On that basis, the experiment in vivo was conducted in this experiment. Eighty Wistar rats were orally exposed to 0 (control group); 0.4 mg/mL (low-dose group); 0.8 mg/mL (mid-dose group) and 1.6 mg/mL (high-dose group) AlCl3 for 120 days, respectively. Aluminum (Al), NE, macrophage migration inhibitory factor (MIF) and tumor necrosis factor-α (TNF-α) contents in serum, cAMP content, β2-AR density, mRNA expressions of TNF-α, MIF and β2-AR in rat peritoneal macrophages were examined. These results showed that AlCl3 increased serum Al and NE contents, peritoneal macrophages cAMP content, the density and mRNA expression of the β2-AR, and decreased serum MIF and TNF-α contents, peritoneal macrophages mRNA expressions of MIF and TNF-α. Serum NE content was negatively correlated with serum TNF-α and MIF contents and peritoneal macrophages mRNA expressions of TNF-α and MIF, but positively correlated with cAMP content, density of β2-AR and mRNA expression of β2-AR of peritoneal macrophages. It indicated that AlCl3 suppresses peritoneal macrophages function of rats through β2-AR/cAMP pathway acted by NE.

NE strengthens the immunosuppression induced by AlCl₃ through β₂-AR/cAMP pathway in cultured rat peritoneal macrophages

To investigate the effect of noradrenaline (NE) on the immunosuppression induced by aluminum trichloride (AlCl3), the peritoneal macrophages were cultured with RPMI-1640 medium containing 0.97 mM AlCl3 (1/10 IC50). NE was added to the medium at the final concentrations of 0 (control group, N-C), 0.1 (low-dose group, N-L), 1 (mid-dose group, N-M), and 10 (high-dose group, N-H) nM, respectively. No addition of both AlCl3 and NE serviced as blank group (D-C). Chemotaxis, adhesion, phagocytosis, tumor necrosis factor α (TNF-α) secretion, cyclic adenosine monophosphate (cAMP) content, β2 adrenergic receptors (β2-AR) density, and messenger RNA (mRNA) expression of macrophages were detected. The results showed that AlCl3 reduced the chemotaxis, adhesion, phagocytosis, and TNF-α secretion and increased the cAMP content, β2-AR density, and mRNA expression of peritoneal macrophages. Meanwhile, the chemotaxis, adhesion, phagocytosis, TNF-α secretion, β2-AR density, and mRNA expression were reduced while the cAMP content was increased in NE-treated groups than those in N-C group. The results indicated that NE strengthens the immunosuppression induced by AlCl3 in cultured rat peritoneal macrophages through the β2-AR/cAMP pathway.

Evaluation of the Pulmonary Toxicity of a Fume Generated from a Nickel-, Copper-Based Electrode to be Used as a Substitute in Stainless Steel Welding

Epidemiology has indicated a possible increase in lung cancer among stainless steel welders. Chromium (Cr) is a primary component of stainless steel welding fume. There is an initiative to develop alternative welding consumables [nickel (Ni)- and copper (Cu)-based alloys] that do not contain Cr. No study has been performed to evaluate the toxicity of fumes generated from Ni- and Cu-based consumables. Dose-response and time-course effects on lung toxicity of a Ni- and Cu-based welding fume (Ni-Cu WF) were examined using an in vivo and in vitro bioassay, and compared with two other well-characterized welding fumes. Even though only trace amounts of Cr were present, a persistent increase in lung injury and inflammation was observed for the Ni-Cu WF compared to the other fumes. The difference in response appears to be due to a direct cytotoxic effect by the Ni-Cu WF sample on lung macrophages as opposed to an elevated production of reactive oxygen species (ROS).

Immunotoxicity of aluminum

Aluminum (Al) is present in the daily life of all humans. With the incidence of Al contamination increased in recent years, the toxicity of Al on the immune function has attracted more attention. Even with this increased attention, the mechanism of Al immunotoxicity still remains unclear. The mechanism of Al immunotoxicity reviewed herein focused on the effects of Al on the splenic trace elements, the status of α-naphthyl acetate esterase (ANAE) cells, cytokines, complement and immunoglobulins, as well as macrophages. The studies in the literature showed that Al decreased splenic iron (Fe) and zinc (Zn) levels, but the effects of Al on splenic copper (Cu) level was ambiguous and controversial. Al exposure inhibited levels of ANAE(+) cells, the production of interleukin (IL)-2 and the functions of macrophages. With respect to other key cytokines, studies showed that Al suppressed the production of tumor necrosis factor (TNF)-α in vitro; effects of Al on TNF-α formation in vivo were less overt. Al exposure reduced complement 3 (C3) level, but effects of Al exposure on complement 4 (C4) level were not as clear-cut. Lastly, the effects of Al exposure on the IgG, IgM and IgA levels were conflicting. Taken in totality, the results of several studies in the literature demonstrated that Al could impart adverse effects on immune function.

Suppressive effects of aluminum trichloride on the T lymphocyte immune function of rats

Aluminum (Al) has increasingly been used in the daily life, and could cause the change of human health because it can accumulate in the organs. A rat model was thus used to examine potential effect of Al on the immune function. Forty male Wistar rats (5 weeks old) weighed 110-120 g were randomly allocated into four groups and were orally exposed to 0, 64.18, 128.36, and 256.72 mg/kg body weight aluminum trichloride (AlCl3) in drinking water for 120 days. The levels of CD3+, CD4+, CD8+ T lymphocyte, acid non-specific activity esterase (ANAE+) in blood, and interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α) in serum were determined at the end of experiment. The results showed that the proportions of CD3+, CD4+ T lymphocyte, the ratio of CD4+/CD8+, and the levels of ANAE+, IL-2, and TNF-α were significantly reduced in AlCl3-treated rats, while the proportion of CD8+ T lymphocyte was increased in an AlCl3-dose dependent manner. Our findings indicate that a long term exposure of AlCl3 could suppress the T lymphocyte immune function of rats.